Radial Magnets, Inc.
Radial Magnets, Inc.we know magnets
Radial Magnets, Inc.
Radial Magnets, Inc.we know magnets
Radial Magnets · Technical Resource
PPAP is a well-documented process and most of it applies to magnets exactly as it applies to anything else. The parts that do not transfer cleanly are the measurement-heavy ones — because a magnet's critical characteristic is a field, fields are harder to measure repeatably than dimensions, and a gauge R&R study on flux behaves nothing like one on a bore diameter.
The Production Part Approval Process is the AIAG-defined method by which a supplier demonstrates, with documented evidence, that its manufacturing process can consistently produce parts meeting the customer's engineering requirements. It is an automotive standard in origin and it remains most rigidly applied there.
Magnets get pulled into PPAP from two directions. Directly, when a magnet is a purchased part in an automotive bill of materials. Indirectly and far more often, when a Tier 2 or Tier 3 supplier building a sensor, actuator, pump or motor is required to flow requirements down to its own component suppliers — and the magnet is a characteristic-defining component in the assembly.
Magnets are frequently bought through distributors who source from more than one mill, and it is entirely possible for parts to arrive to the same print, to the same grade, from a different factory, without anyone flagging it. Under PPAP that is a process change requiring resubmission. If you are the customer, state the approved manufacturing location explicitly on the PSW and require notification of any change. If you are specifying, this is a good reason to know which mill your parts come from — see second-source qualification.
| Level | What is submitted | Typical trigger |
|---|---|---|
| Level 1 | PSW only, with appearance approval where applicable | Low-risk or appearance-only items |
| Level 2 | PSW plus product samples and limited supporting data | Established supplier, established part family |
| Level 3 | PSW plus samples and complete supporting documentation | The default for magnets. New part, new supplier, design change |
| Level 4 | PSW plus whatever the customer specifically defines | Programme-specific requirements |
| Level 5 | PSW plus samples and full records reviewed on site | Safety-critical parts, new supplier qualification |
Level 3 is what a magnet programme should plan for unless the customer has said otherwise in writing. Assuming Level 2 and being asked for Level 3 late is one of the more reliable ways to lose four weeks.
Level 5 requires records to be reviewed at the manufacturing location. Where sintering happens overseas, that means an on-site audit at the mill, with travel, scheduling and language logistics attached. If a programme is heading toward Level 5, raise it at sourcing rather than at submission — it can add months and it may influence which mill is the right choice.
The standard eighteen elements all apply. These are the ones where magnets behave differently from machined or moulded parts and where submissions most often come back with findings.
For sintered NdFeB the flow is long and includes several steps with no visual output: incoming alloy, hydrogen decrepitation, jet milling, aligned pressing, vacuum sintering, ageing heat treatment, machining and grinding, coating, magnetising, inspection, packing. The flow must extend back through sub-contracted operations — plating in particular is very often an outside process, and it has to appear on the diagram and in the control plan.
The high-severity failure modes specific to magnets:
Magnet control plans need controls the generic template does not prompt for: material traceability to alloy lot; sintering furnace profile records; magnetising fixture verification with peak field logged; flux or surface field measurement with the fixture and location defined; coating thickness and adhesion; and dimensional inspection stated as after-coating.
“Surface gauss 4200 ±5 %” is not a controllable characteristic. Surface field depends entirely on where the probe sits, how it is held, what backing iron is present and how the part is fixtured — two labs can measure the same magnet and differ by more than the tolerance band. A magnetic characteristic on a control plan must specify the method, the fixture, the probe location and the reference condition, or it is not measurable and the gauge study will prove it. See how magnets are tested.
This is where magnet PPAPs actually fail, and it is worth understanding before the study is run rather than after.
A Helmholtz coil and fluxmeter measure total magnetic moment of the whole part and are far less sensitive to positioning than a Gaussmeter probe on a surface. Where a magnetic characteristic has to be demonstrated capable, total flux in a Helmholtz fixture will usually pass a gauge study that surface gauss cannot. The trade is that total moment is not always the characteristic the application cares about — but it is often close enough to be the right control, with surface field checked at a lower frequency as a correlation.
Customers typically expect Ppk ≥ 1.67 on significant characteristics at submission, moving to an ongoing Cpk requirement in production. For magnets, plan on:
Which characteristics should carry capability requirements at all is a decision worth making deliberately — see tolerances and acceptance criteria.
A Level 3 magnet PPAP runs roughly eight to sixteen weeks from approved drawing to PSW submission, assuming the first production run yields conforming parts. Assuming means it usually does not.
| Stage | Typical duration | Where it slips |
|---|---|---|
| Drawing and specification agreement | 1–3 weeks | Magnetic acceptance criteria left undefined |
| Tooling and magnetising fixture | 3–8 weeks | Radial and multipole fixtures are custom builds |
| Significant production run | 2–4 weeks | Mill campaign scheduling, not machine time |
| Coating (often sub-contracted) | 1–2 weeks | Outside process; adds a queue and a shipping leg |
| MSA studies | 2–3 weeks | The magnetic gauge study, reliably |
| Documentation and internal review | 1–2 weeks | Sub-tier documents missing |
| Customer review and disposition | 1–4 weeks | Outside your control entirely |
PPAP requires parts from a run made with production tooling, production process and production operators — commonly 300 pieces or more, across shifts. For magnets that means a genuine mill campaign, and mills schedule campaigns by alloy and grade rather than by customer. A small PPAP quantity may wait for the next run of that grade regardless of how urgent the programme is. This constraint is invisible on a project plan built from machining assumptions, and it is the most common reason magnet PPAPs run late.
Where PPAP sits alongside the other documentation you may be asked for — certificates of conformance, material declarations, RoHS and REACH — is covered in certificates and compliance documents.
We have completed Level 3 submissions for automotive programmes including sensor and motor ring assemblies, and we maintain documentation packages with traceability to mill. Send us the part and the customer requirement and we will build a realistic timeline.